Twin convenience outlet and cap with third wire ground



P. HUTT Aug. 10, 1954 TWIN CONVENIENCE OUTLET AND CAP WITH THIRD WIRE GROUND Filed Oct. 31, 1950 Patented Aug. 10, 1954 TWIN CONVENIENCE OUTLET AND CAP WITH THIRD WIRE GROUND Philip Hutt, Milford, Conn., assignor to General Electric Company, a corporation of New York Application October 31, 1950, Serial No. 193,060

6 Claims. 1

This invention relates to an improved convenience outlet and attachment cap for third wire grounding of electrical equipment.

In the operation of electrical equipment such as portable tools, washing machines, and food mixers, it is important to provide a grounding connection from the frame or exposed conducting portions of such equipment as a protection against the hazard of electrical shock. The means heretofore available for grounding have not been convenient to use, or suiiiciently reliable.

In the arrangement to which this invention is related, the convenience outlet provides an electrical connection to the metallic armor of metallic armored cable, or to a conduit, or to a separate grounding conductor, of the wiring system. The attachment cap has an additional pin or blade for connection by a separate conductor to the frame or exposed conducting portions of the equipment. It is important that the pin or blade on the cap be reliably connected through means provided in the convenience outlet to whatever part of the electrical system is used for grounding.

It is an object of this invention, then, to provide an improved means for facilitating the grounding of an appliance through a convenience outlet.

It is a further object of this invention to provide a new and improved cap engageable with the convenience outlet to facilitate the grounding of appliances.

It is a further object of this invention to provide, in a convenience outlet, contact between a grounding pin in a cap and the mounting strap for the twin convenience outlet.

It is a further object of this invention to provide a better contact between the grounding pin of the cap and the mounting strap of the convenience outlet by inserting a spring in the mounting strap for contact with the grounding pm.

It is a still further object of this invention to provide an improved twin convenience outlet wherein the ground wire binding screws are in front and are visible for the determination of whether or not the ground wire is connected.

Further objects and advantages of this invention will become apparent and the invention will be more clearly understood from the following description referring to the accompanying drawing and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In the drawing, Fig. 1 is a front elevation of the twin convenience outlet with a cap inserted into the upper of the outlets; Fig. 2 is a side elevation of the twin convenience outlet and cap shown in Fig. 1; Fig. 3 is a cut-away portion of the twin convenience outlet and cap as shown in Fig. 2; Fig. 4 is an exploded view of the elements that make up the twin convenience outlet; while Fig. 5 is a back view of a portion of the twin convenience outlet, and Fig. 6 is a bottom view of the cap shown in Figs. 1 and 2.

Broadly, this invention comprises an improved convenience outlet having a mounting strap with improved contacts engageable with a grounding prong on the cap and further having lateral abutments for the positioning of binding screws for the grounding wire.

In the drawing, a twin convenience outlet or receptacle i is shown comprising a mounting strap 2, an insulating body portion 3, and a top cooperating member or cover 4. A cap 5 is shown in engagement with the twin convenience outlet in Figs. 1, 2, and 3 of the drawing.

The body portion 3 is formed with cavities 3a and 31; positioned on both sides of a central dividing wall 30. In these cavities, blade-receiving spring contact elements 32 are frictionally positioned, as hereinafter further described.

Mounting strap 2 is formed from a conventional type of metal used generally for mounting switches and outlet boxes and the like. It is capable of being stamped or pressed into any desired shape. Preferably, however, it is provided with ears 5, each containing an aperture to provide for the mounting of the strap in a conventional outlet box (not shown). The mounting strap is further provided with a pair of binding screws 8 which are mounted in lateral abutments 9 formed on the mounting strap. The lateral abutments are provided with a threaded bore for engaging the binding screws 3. The mounting strap further has a pair of apertures I 0 which are most clearly shown in the exploded view of Fig. 4. Each of the apertures i is substantially rectangular but has provided in oppo site sides thereof a V-shaped protrustion H which acts as stops for a spring contact !2. The spring contacts [2 are U-shaped pieces of flexible metal inserted through the aperture it so as to be retained by one end wall thereof and the V-shaped protrusion ll. With this method of securing the contact element 5 2, better contact is established with the cap in the manner that will hereinafter be described.

The body portion 3 is preferably molded of the usual phenolic resin or other suitable ininsulating material shaped to the conventional contours, and is provided with apertures l3 and M to house screws 15 and I6, respectively, for securing the body portion to the outlet. The body portion further defines a pair of cavities ii and it for housing the contacts l2 which are positioned in the mounting strap 2, as has heretofore been described. The contacts l2 are thus completely isolated by insulating walls from the line contact elements 32.

The body portion further defines bores IQ for accommodating the grounding binding screws 8, whereby the ends of the screws are also completely isolated by insulating walls from the line contact elements 32.

Cover portion 4, like the body portion 3, is preferably molded from phenolic resin or the like contoured to be complementary to the body portion to form a complete outlet with the strap 2.

Cover portion 4 is provided with cavities, bores,

portions 26 of the conventional type which further have an aperture 2! for accommodating a grounding pin therethrough intengagement with the spring contacts [2. It is important to note at this point that the cover portion 5 is cutaway to provide two portions 22 and 23 to lay bare the binding screws 8. With this structure, the binding screws are within view from the front of the convenience outlet and, consequently, it can be determined visually whether or not ground wires are connected to the binding screws 8. In this manner, an inspector can readily determine Whether or not the ground wire is connected without removing the outlet from the box in which it is mounted.

The cap 5, while being of the usual male type having two contact blades thereon, is further provided with a pin 24 which may be circular or D-shaped in cross section to be engageable with the springs i2 after being passed through the apertures 2! in the cover plate 4. It i important to note that a, clamp 25, which is provided on the cap for engaging the conductor leading to the appliance, is formed in two halves, for example, 26 and 21. One of these clamp halves; specifically, the half 26, is secured to the cap 5 by means of the pin 24, which, in addition to acting as the grounding pin, further has the function of acting as a rivet for securing the half of the clamp 26 to the cap. The complementary half of the clamp 2'! is secured by a rivet 28. With this structure, the two halves of the clamp 25 are rotatable about the supporting pins or rivets to open up and to close about a conductor; the halves can then be secured together by means of screws 29 to provide a rigid structure.

A further feature of this invention resides in the structure of the wire clamping means. The body portion 3 of the receptacle i is provided with cavities 3a, 319, wherein spring contact elements are frictionally positioned one on each side of a central dividing wall 30. As shown in Fig. 4, each of the spring contact elements is provided with a binding screw 33 passing through an aperture in a portion of the spring contact element and threaded into a clamp 34. The clamp 34 is a substantially rectangular dished washer having two rounded slots 35 and 35 adapted to engage conductors of the wiring system. The back wall of the body portion 3 is provided with pairs of apertures 30 and 3!, which apertures are positioned beneath the respective binding screws 33 of the spring contact elements 32. One of the apertures, for example, the aperture 30, is opened through the side wall of the body 3 to form a slot therein. With this structure, the receptacle may be back wired by pushing conductors through both back openings 36 and 3! into the slots 35 and 35 of the clamping element 3t whereby when the screw 33 is tightened the clamp securely holds the wires in contact with the contact element 32. If desired, a conductor may also be secured from the side of the receptacle beneath the head of the terminal screw 33. It will be observed that my construction not only provides for both side wiring and back Wiring of the receptacle, but also provides for the connection of two conductors to each terminal screw, whereby a number of these twin convenience outlets can easily be wired into one circuit and yet onl a single terminal screw is required instead of two screws, as heretofore used.

Modifications of this invention. will occur to those skilled in the art and it is desired to be understood, therefore, that this invention is not intended to be limited to the particular embodiment disclosed, but that it is meant to cover all modifications which are within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A convenience outlet comprising an insulating body portion, a mounting strip, and contact means on said mounting strap to provid a grounding connection for an attachment cap, said contact means comprising an aperture defined by mounting strap, and a U-shaped spring contact positioned in said aperture to extend perpendicularly to said mounting strap, the side walls or" said aperture having protrusions thereon to position the legs of said spring con" tacts between said protrusions and one end wall of said aperture.

2. An outlet for providing an electrical grounding connection comprising an insulating body portion, line contact channels formed in said body portion to house said line contact means, a longitudinal wall dividing said channels, said longitudinal wall defining centrally disposed insulated recesses, a mounting strap of conductive material engageable with said body portion, said mounting strap having apertures registering with. said insulated recesses, spring contacts supported by said mounting strap in the apertures thereof and extending one into each of said insulated recesses, a cover engageable with said body portion and said mounting strap, said cover defining apertures registering with said mounting strap apertures whereby a prong contact can pass through one of said cover apertures and through one of said mounting strap apertures to be engageable with said spring contact means.

3. A convenience outlet for providing a grounding connection in an electrical circuit comprising an insulated body portion, a mounting strap engageable with said body portion and adapted to be connected to a ground potential, said mounting strap defining apertures for receiving a grounding prong, spring contact means positioned in said apertures and adapted to be engaged by a grounding prong, a cover engageable with said body portion substantially to enclose said mounting strap, lateral abutments on said strap each having a threaded bore and a binding screw engageable therewith to provide means for connecting said mounting strap to a ground potential, said cover having portions cut away to expose said binding screws to give a visual indication of a ground connection.

4. A convenience outlet comprising a recessed body member of insulating material, a mounting strap of conductive material secured to said member and adapted to be connected to a grounding potential, said body member having insulating walls forming a plurality of recesses insulated from each other, spring contact blades in some of said recesses adapted to receive contact blades of an attachment cap, said mounting strap having an aperture therein, spring contact means supported by said mounting strap to lie within said aperture, and extending into another of said recesses and adapted to be engaged by a grounding prong on an attachment cap, and binding screws threaded into said mounting strap and extending into still other recesses of said body member for connecting said mounting strap to a ground potential.

5. The combination of a convenience outlet and an attachment cap therefor, said outlet comprising an insulating body portion, a mounting strap, and contact means positioned by said mounting strap to provide a grounding connection for said attachment cap, said contact means comprising an aperture defined by said mounting strap and a U-shaped spring contact positioned in said aperture to extend perpendicularly to said mounting strap, the side walls of said aperture having protrusions thereon to position the legs of said spring contacts between said protrusions and one end wall of said aperture, said attachment cap comprising a clamp, a body portion and a prong engageable with said U-shaped contact, and means for securing said clamp to said prong and body portion comprising a rivet integral with said prong and extending coaxially therewith through said clamp.

6. A convenience outlet including an insulating body portion, a mounting strap therefor and means for providing a grounding connection between a prong of an attachment cap and said mounting strap, said means comprising bottom and side walls in said body portion positioned in proximity to an aperture in said mounting strap to define a prong receiving cavity, and a spring contact element having portions abutting the bottom and a side wall of said cavity and a portion protruding through said aperture to engage a portion of the periphery thereof to be held in position and in contact with said mounting strap by its inherent spring tension, said aperture and said cavity being shaped to receive a prong of an attachment cap for contacting said spring contact element.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,672,067 La-bre June 5, 1928 1,78 ,527 Bennett Nov. 25, 1930 1,891,153 Gates Dec. 13, 1932 1,975,820 Wright Oct. 9, 1934 2,174,773 Blood Oct. 3, 1939 2,262,712 Shenton Nov. 11, 1941 2,292,084 Pistey Aug. 4, 1942 2,315,523 Hubbell Apr. 6, 1943 2,586,696 Nauth Feb. 19, 1952 FOREIGN PATENTS Number Country Date 51,011 Switzerland Apr. 15, 1910 154,312 Switzerland Apr. 30, 1932 

